<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<input type="button" value="点我" id="btn">
<script>
    var btn = document.getElementById('btn');
    btn.onclick = function(){
       ~function(){
           console.log(this)
           this.value = 'clickMe'
       }.call(this)
    }
</script>
</body>
</html>